1. Field of the Invention
This invention relates to control circuitry for correcting error in the rate of change of frequency of an oscillator output signal. The circuitry is particularly suitable for use in an FMCW radar transmitter, but the invention is not limited either to this application or, indeed, to oscillators operating only at radio frequencies.
2. Description of Related Art
Many radar and communication systems require the transmission of a carrier wave of continuously changing frequency. In particular, a constant rate of change of frequency is often desirable, i.e. a linear frequency-time waveform, as used, for example, in FMCW radars. In such radars it is necessary to correct any non-linearities in the frequency sweep of the transmit oscillator if good target range resolution is to be achieved. Correction of such non-linearities thus reduces errors likely to result in a target being allocated to an incorrect range bin.